Synthetic hosts transport medical substances and hormones into the body and release them at specific points. They enclose the active substances in a cavity. In the case of steroids, this task has been accomplished mainly by ring-shaped glucose molecules. Now, scientists of KIT and Jacobs University Bremen have discovered a new class of host molecules, barrel-shaped cucurbiturils. They can make mostly insoluble steroids, such as cortisone or estradiol, act more gently and more efficiently.